The proposal consists of four parts: (1) A preliminary quantitative study of the so-called "barrel" field of the mouse somatosensory cortex in normal adult animals and in mice from which groups of mystacial vibrissae were removed shortly after birth. In this part of the work we hope to determine the optimum conditions for Golgi impregnation and to evaluate a number of computer-based methods for measuring a variety of neuronal parameters (e.g., lengths of branching patterns of dendrites, numbers of dendritic spines, etc.); (2) A series of studies of the development of the visual system, using the domestic chick as the experimental model. These studies are concerned principally with the degree of specificity in the projection of the retinal ganglion cells upon the optic tectum, and the extent to which the developing retino-tectal system may adjust to various experimental manipulations, and to determine to what extent errors occur in the system during its normal development; (3) To analyze the effects of visual deprivation or eye removal upon the maturation of certain of the visual relay centers within the brain, using the automated computer system for counting silver grains and autoradiographs; (4) The development of a series of new computer programs and associated hardware for the quantitative analysis of morphological data, including programs for the counting and graphic display of dendritic spines, for grain counting in autoradiographs, and for classifying neurons on a metric basis. BIBLIOGRAPHIC REFERENCES: Clarke, P. G. H., L. A. Rogers and W. M. Cowan 1976. The time of origin and the pattern of survival of neurons in the isthmo-optic nucleus of the chick. J. Comp. Neur., 167: 125-141. Clarke, P. G. H., and W. M. Cowan 1976. The development of the isthmo-optic tract in the chick with special reference to the occurrence and correction of developmental errors in the location and connections of isthmo-optic neurons. J. Comp. Neur., 143-163.